Cartridge Bearings for me everytime.
When I first started mountaining biking I bought a bike that had Shimano Deore hubs, I was forever working on the hubs, the bearings and cones seem to wear very quickly, they definately didn't like Scottish off road conditions, now using Hope hubs on both bikes, and I've changed one set of rear bearings in the last two years, everything else is still super smooth. The freehubs are also much easier to repair on the cartridge bearing hubs.